1. Field of the Invention
The present invention relates to a laser processing apparatus in which a laser beam which is guided to the inside of a processing head by a laser oscillator is converged by a converging lens of the processing head, and is guided onto a material to be processed such as a metal plate, plastic plate, or the like, and thereby processing such as cutting, welding, or the like of the material to be processed is performed.
Priority is claimed on Japanese Patent Application No.2004-138324 filed May 7, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
Generally, a laser processing apparatus is known in which, using the laser beam, processing such as cutting, welding, or the like of a material to be processed is performed in order to form a predetermined shape of product.
Here, because a diameter of the laser beam changes according to an optical path length, that is, the diameter of the laser beam is increased according to increase of the optical path length, the optical path length from the laser oscillator to the processing head strongly affects to the processing performance in the case of the laser processing. Moreover, the optical path length which is needed differs according to parameters of the processing method such as whether nitrogen gas is used as an assist gas, whether oxygen gas is used as an assist gas, whether edge preparation is performed, and whether three dimensional processing in which a mirror is arranged under the converging lens is performed, and according to the quality of the material to be processed, for example iron or a soft steel material which is, for example stainless material, or the like, and according to the thickness of the material to be processed, and the like.
Therefore, a long optical path length may be needed according to the processing method, and the quality, the thickness, or the like of the material to be processed.
However, in laser processing, in order to prevent the laser processing apparatus from becoming large, generally, a compact size of laser processing apparatus corresponding to the size of the material to be processed is used, and thereby it is difficult for a long optical path length to be obtained.
In order to solve the above problem, and to obtain a long optical path length, generally, a laser processing apparatus which is provided with a laser light reversal apparatus by which the laser light from the laser oscillator is reversed, and then enters the processing head is known (see Patent Document 1: Japanese Examined Patent Application, Second Publication No. H1-55076).
However, in this laser processing apparatus, the laser light from the laser oscillator is reversed once, and enters the processing head, and therefore, the optical path length is restricted by the effective processing width of the laser processing apparatus, and increase of the optical path length is limited.
Because of this, due to the processing method, quality of the material, or thickness of the material to be processed, proper processing performance cannot to obtained, and in order to obtain proper processing performance with a short optical path length, for example, when a thin plate is processed, a converging lens whose focal length is short is needed, and it is necessary for the converging lens to be positioned near the thin plate, and so a problem occurs in which, the spatter (a melted part of the material to be processed) or hume (material which is melted and then solidified) which is scattered during processing adheres to the converging lens.
Moreover, in order to increase the optical path length, generally, a laser processing apparatus is known in which the laser oscillator and the reversal mirror body are arranged on the inside of a main frame, and the reversal mirror body is moved within the main frame, and thereby the optical path length is adjusted within the main frame, and the optical path length from the laser oscillator to the processing head can be changeably set to the proper optical path length according to change in the thickness or quality of the material to be processed (for example, see Patent Document 2: Japanese Patent No. 3084780).
Moreover, a laser processing apparatus is known in which the laser light emitted from the laser oscillator is reflected in a rail laying direction by a first reflection member, is reversely reflected in a direction parallel to the direction of the rail by a reversal apparatus, is reflected in the direction of a torch by the second reflection member, is condensed by a lens via a mirror which is provided at the torch, and is emitted onto the material to be processed, and the reversal apparatus is movable in the rail laying direction, and thereby the setting of the optical path length can changed (for example, see Patent Document 3: Japanese Examined Patent Application, Second Publication No. H5-49396).
However, in a laser processing apparatus of conventional technology in which a reversal mirror body is movable within the main frame, and thereby the optical path length within a main frame is adjusted, in order to increase the optical path length and to adjust the optical path length, it is necessary for a reversal mirror body which has a plurality of mirrors to be provided on the inside of the main frame in which the laser oscillator is provided, and a mechanism which renders the reversal mirror body movable is needed, and thereby the structure of the laser processing apparatus becomes complicated, and it becomes large in size. Especially, in order to prevent danger from the laser light, it is necessary for the structure of the reversal mirror body and the movement mechanism of the reversal mirror body to be extremely precise, and thereby the constitution thereof is complicated. Moreover, in this laser processing apparatus, after the laser light emitted from the laser oscillator is reflected in the vertical direction on the way, the laser light enters the processing head, and thereby the laser processing apparatus becomes large in size.
Moreover, in the laser processing apparatus of conventional technology in which the laser light emitted from the laser oscillator enters the torch via the first reflection member, reversal apparatus, and second reflection member, and the reversal apparatus for changing the optical path length is movable in the rail laying direction, it is necessary for the first reflection member to be provided at the backside of the laser oscillator. Further, in order to move the first reflection member, it is necessary to provide a holder, rail, or the like which is extended in the vertical direction with respect to the movement direction of the torch, and the constitution of the laser processing apparatus is complicated, and becomes large in size. Especially, in order to prevent danger from the laser light, it is necessary for the structure of the first reflection member and of the holder, rail, or the like of the first reflection member to be extremely precise, and thereby the constitution thereof is complicated. Moreover, because the material to be processed cannot be arranged under the first reflection member, a problem occurs in which the effective processing width of the laser processing apparatus becomes low.